Structured Adsorbent Beds, Methods of Producing the Same and uses Thereof

ABSTRACT

Structured adsorbent beds comprising a high cell density substrate, such as greater than about 1040 cpsi, and a coating comprising adsorbent particles, such as DDR and a binder, such as SiO 2  are provided herein. Methods of preparing the structured adsorbent bed and gas separation processes using the structured adsorbent bed are also provided herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/953,648 filed Nov. 30, 2015 entitled STRUCTURED ADSORBENT BEDS,METHODS OF PRODUCING THE SAME AND USES THEREOF, and claims priority toU.S. Provisional Application Ser. No. 62/119,458 filed Feb. 23, 2015 andto U.S. Provisional Application Ser. No. 62/096,137 filed Dec. 23, 2014,which are herein incorporated by reference in their entirety.

FIELD

The present invention relates to structured adsorbent beds forpurification of gas feedstreams and methods of making such structuredadsorbent beds. The structured adsorbent beds comprise a substrate witha high cell density and a coating on the substrate, wherein the coatingcomprises adsorbent particles and a binder.

BACKGROUND

Gas separation is important in many industries for removing undesirablecontaminants from a gas stream and for achieving a desired gascomposition. For example, natural gas from many gas fields can containsignificant levels of H₂O, SO₂, H₂S, CO₂, N₂, mercaptans, and/or heavyhydrocarbons that have to be removed to various degrees before the gascan be transported to market. It is preferred that as much of the acidgases (e.g., H₂S and CO₂) be removed from natural gas as possible toleave methane as the recovered component. Small increases in recovery ofmethane can result in significant improvements in process economics andalso serve to prevent unwanted resource loss. It is desirable to recovermore than 80 vol %, particularly more than 90 vol %, of the methane whendetrimental impurities are removed.

Additionally, synthesis gas (syngas) typically requires removal andseparation of various components before it can be used in fuel, chemicaland power applications because all of these applications have aspecification of the exact composition of the syngas required for theprocess. As produced, syngas can contain at least CO and H₂. Othermolecular components in syngas can be CH₄, CO₂, H₂S, H₂O, N₂, andcombinations thereof. Minority (or trace) components in the gas caninclude hydrocarbons, NH₃, NO_(x), and the like, and combinationsthereof. In almost all applications, most of the H₂S should typically beremoved from the syngas before it can be used, and, in manyapplications, it can be desirable to remove much of the CO₂.

Adsorptive gas separation techniques are common in various industriesusing solid sorbent materials such as activated charcoal or a poroussolid oxide such as alumina, silica-alumina, silica, or a crystallinezeolite. Adsorptive separation may be achieved by equilibrium or kineticmechanisms. A large majority of processes operate through theequilibrium adsorption of the gas mixture where the adsorptiveselectivity is primarily based upon differential equilibrium uptake ofone or more species based on parameters such as pore size of theadsorbent. Kinetically based separation involves differences in thediffusion rates of different components of the gas mixture and allowsdifferent species to be separated regardless of similar equilibriumadsorption parameters.

Kinetically based separation processes may be operated as pressure swingadsorption (PSA), temperature swing adsorption (TSA), partial pressureswing or displacement purge adsorption (PPSA) or as hybrid processescomprised of components of several of these processes. These swingadsorption processes can be conducted with rapid cycles, in which casethey are referred to as rapid cycle thermal swing adsorption (RCTSA),rapid cycle pressure swing adsorption (RCPSA), and rapid cycle partialpressure swing or displacement purge adsorption (RCPPSA) technologies,with the term “swing adsorption” taken to include all of these processesand combinations of them.

Traditionally, adsorptive separation processes use packed beds ofadsorbent particulates. However, the traditional packed beds are notlikely to meet the very stringent requirements for natural gas cleanup.Alternatively, a structured adsorbent bed can be utilized to adsorbcertain gas species. The structured adsorbent bed can be a monolith,either in the form of one single block or in the form of extrudates withmultiple channels or cells, such as a honeycomb structured monolith. Theuse of adsorbent monoliths provides one approach to designing anadsorbent bed that has low pressure drop, good flow distribution, andlow dispersion. Monoliths have very low flow tortuosity and can also beengineered for almost any user specified void volume to meet a specifiedpressure drop. Other monolith advantages include avoidance of bedfluidization or lifting. In addition to gas separation processes, thesetypes of monoliths have historically been employed as catalyst supportsin automobile catalytic converters, catalytic combustion,electrochemical reactors and biochemical reactors.

In order to prepare the monoliths for use in gas separation processes oras catalyst supports, the cells are washcoated with layers of catalyticor adsorbent coatings. The cell density of the monolith and the size ofthe particles in the coating have a significant effect on the ability tosuccessfully coat the cells in the monolith to provide a structuredadsorbent bed. It is known that coating difficulty increases as the celldensity of the monolith increases (i.e., the channel size of themonolith decreases), as the size of the particles in the coatingincreases over 2 μm, as the number of coatings increase and as substrateporosity decreases toward zero porosity. For example, Agrafiotis, C. etal. report that the size of the suspended particles affects the adhesionof the washcoat on the substrate, namely particles with a diameter ofless than 2 μm have increased adhesion to a monolith with a cell densityof 400 cells per square inch (cpsi) than larger diameter particles. J.Mater. Sci. Lett., 18:1421-1424 (1999). Thus, typically the monolithsused in practice have lower cell densities (e.g., 300-900 cpsi), thecoatings contain small particles (e.g., diameter less than 2 μm) and/orthe coating is applied in very thin layers (e.g., 1 μm to 10 μm). Forexample, while U.S. Pat. No. 6,936,561 reports a coating layer thicknessabove 300 μm on a ceramic honeycomb monolith, the monolith has a lowcell density of about 45 cpsi. Similarly, U.S. Pat. No. 7,560,154reports a method of manufacturing a honeycomb structure with a coatingparticle size of 15 to 75 μm, but the cell density of the structure is260 cpsi.

However, kinetic separation processes, specifically rapid cycle kineticseparation processes require structured adsorbent beds with ultra highcell density (i.e., greater than 1000 cpsi) and thicker coating layers.Furthermore, larger particle sizes in the coating are desirable becausefurther milling to reduce the particle size can be avoided, therebyavoiding potential fracturing of the particles which can result indiminished capacity and activity. Therefore, there is a need to providestructured adsorbent beds with ultra high cell density as well asthicker coating layers and larger particles sizes in the coating.

SUMMARY

It has been found that a structured adsorbent bed for purification of agas feedstream comprising a substrate having a high cell density (e.g.,greater than 1040 cpsi), and a coating on the substrate, wherein thecoating comprises large adsorbent particles (e.g., an average diametergreater than 20 μm) and a binder, can be achieved by pretreating thesubstrate prior to applying the adsorbent particles and binder.

Thus, in one aspect, embodiments of the invention provide a structuredadsorbent bed for purification of a gas feedstream comprising: asubstrate having a cell density greater than 1040 cpsi; and a coating onthe substrate, wherein the coating comprises adsorbent particles and abinder.

In still another aspect, embodiments of the invention provide a methodof preparing the structured adsorbent bed described herein, the methodcomprising: pretreating the substrate; preparing an aqueous slurrycomprising the adsorbent particles and the binder; and applying theaqueous slurry to the substrate to form the coating on the substrate.

In still another aspect, embodiments of the invention provide a gasseparation process comprising contacting a gas mixture containing atleast one contaminant with an adsorbent bed described herein.

Other embodiments, including particular aspects of the embodimentssummarized above, will be evident from the detailed description thatfollows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of the distances used for determining theaxis ratio of an adsorbent particle in a scanning electron microscope(SEM) image.

FIGS. 2a and 2b illustrate SEM images for a 2700 cpsi ceramic monolith.

FIG. 3 illustrates a Leica Optical scope picture with 40× magnificationof a 1440 cpsi 315 stainless steel monolith after 900° C. calcination.

FIGS. 4a and 4b illustrate a transmission electron microscopy (TEM)image and size analysis results showing average diameter of the binder,25 nm colloidal SiO₂.

FIGS. 5a and 5b illustrate TEM image and size analysis results showingaverage diameter of the binder, 100 nm colloidal SiO₂.

FIGS. 6a and 6b illustrate a TEM image and size analysis results showingaverage diameter of the binder, string of pearls colloidal SiO₂.

FIG. 7 illustrates a Leica Optical scope picture (40× magnification) ofa 1440 cpsi metal monolith after 4 coatings with DDR (25-30 μm) and SiO₂(100 nm).

FIG. 8 illustrates an SEM image of a DDR (25-30 μm) and SiO₂ (100 nm)coating on a 1440 cpsi metal monolith and/or glass slide after 500° C.calcination.

FIG. 9 provides photographs of the 25-2-2, 26-6-2, 26-7-3, 26-8-23 and25-4-23 coupons with coating prior to integrity testing.

FIG. 10 illustrates a 26-8-23C coupon before integrity testing (topphotograph) and after integrity testing (bottom photograph).

FIG. 11 illustrates a 25-4-23C coupon before integrity testing (topphotograph) and after integrity testing (bottom photograph).

FIG. 12 illustrates a 26-7-3C coupon before integrity testing (topphotograph) and after integrity testing (bottom photograph).

FIG. 13 illustrates test button D before (left photograph) and after(right photograph) adsorptive kinetic separation (AKS) integritytesting.

FIG. 14 illustrates weight of test button D as superficial gas velocityincreases during AKS integrity test.

FIG. 15 illustrates zero length chromatography (ZLC) results comparing aDDR adsorbent (without binder) to SiO₂ bound DDR samples with a DDR:SiO₂weight ratio of 85:15 w/w.

FIG. 16 illustrates ZLC results comparing a DDR adsorbent (withoutbinder) to SiO₂ bound DDR samples with a DDR:SiO₂ weight ratio of 90:10w/w.

DETAILED DESCRIPTION

In various aspects of the invention, structured adsorbent beds, methodsof preparing the structured adsorbent beds and gas separation processesusing the structured adsorbent beds are provided.

I. Definitions

To facilitate an understanding of the present invention, a number ofterms and phrases are defined below.

As used in the present disclosure and claims, the singular forms “a,”“an,” and “the” include plural forms unless the context clearly dictatesotherwise.

Wherever embodiments are described herein with the language“comprising,” otherwise analogous embodiments described in terms of“consisting of” and/or “consisting essentially of” are also provided.

The term “and/or” as used in a phrase such as “A and/or B” herein isintended to include “A and B”, “A or B”, “A”, and “B”.

As used herein, the term “adsorption” includes physisorption,chemisorption, and condensation onto a solid support and combinationsthereof.

The term “monolith” refers to any three-dimensional material that cancontain numerous parallel channels per square inch and can serve as asupport for adsorbents or catalysts, such as solid pieces of metal orceramic materials or honeycomb structures. The term monolith is meant tobe distinguished from a collection of individual particles packed into abed formation, in which the end product comprises individual particles.

As used herein, the term “average diameter” of the particle refers tothe number average of the major axis and minor axis.

As used herein, the term “porosity” refers to a measure of the voidspaces in a material, and is measured herein as percent between zero and100%.

As used herein, the term “macroporosity” refers to the percentage ofpores in a material that have a diameter greater than 50 nm.

As used herein, the term “microporous” refers to solid materials havingpores with a diameter less than 2 nm.

As used herein, the term “Si/Al ratio” is defined as the molar ratio ofsilica to alumina of a zeolitic structure.

II. Structured Adsorbent Bed

In a first embodiment a structured adsorbent bed for purification of agas feedstream is provided comprising a substrate and a coating on thesubstrate.

A. Substrate

As discussed above, substrates traditionally have a lower cell densitybecause as cell density of the substrate increases and the channels inthe bed decrease in size, difficulty in coating the substratesincreases. However, substrates, such as monoliths, with higher celldensity are provided herein. In various aspects, the substrate has acell density of greater than or equal to about 900 cpsi, greater than orequal to about 920 cpsi, greater than or equal to about 940 cpsi,greater than or equal to about 960 cpsi, greater than or equal to about980 cpsi, greater than or equal to about 1,000 cpsi, greater than orequal to about 1,020 cpsi, greater than or equal to about 1,040 cpsi,greater than or equal to about 1,060 cpsi, greater than or equal toabout 1,080 cpsi, greater than or equal to about 1,100 cpsi, greaterthan or equal to about 1,120 cpsi, greater than or equal to about 1,140cpsi, greater than or equal to about 1,160 cpsi, greater than or equalto about 1,180 cpsi, greater than or equal to about 1,200 cpsi, greaterthan or equal to about 1,220 cpsi, greater than or equal to about 1,240cpsi, greater than or equal to about 1,260 cpsi, greater than or equalto about 1,280 cpsi, greater than or equal to about 1,300 cpsi, greaterthan or equal to about 1,320 cpsi, greater than or equal to about 1,340cpsi, greater than or equal to about 1,360 cpsi, greater than or equalto about 1,380 cpsi, greater than or equal to about 1,400 cpsi, greaterthan or equal to about 1,420 cpsi, greater than or equal to about 1,440cpsi, greater than or equal to about 1,460 cpsi, greater than or equalto about 1,480 cpsi, greater than or equal to about 1,500 cpsi, greaterthan or equal to about 1,520 cpsi, greater than or equal to about 1,640cpsi, greater than or equal to about 1,760 cpsi, greater than or equalto about 1,880 cpsi, greater than or equal to about 1,900 cpsi, greaterthan or equal to about 1,920 cpsi, greater than or equal to about 1,940cpsi, greater than or equal to about 1,960 cpsi, greater than or equalto about 1,980 cpsi, greater than or equal to about 2,000 cpsi, greaterthan or equal to about 2,100 cpsi, greater than or equal to about 2,200cpsi, greater than or equal to about 2,300 cpsi, greater than or equalto about 2,400 cpsi, greater than or equal to about 2,500 cpsi, greaterthan or equal to about 2,600 cpsi, greater than or equal to about 2,700cpsi, greater than or equal to about 2,800 cpsi, greater than or equalto about 2,900 cpsi, greater than or equal to about 3,000 cpsi, greaterthan or equal to about 3,100 cpsi, greater than or equal to about 3,200cpsi, greater than or equal to about 3,300 cpsi, greater than or equalto about 3,400 cpsi, greater than or equal to about 3,500 cpsi, greaterthan or equal to about 3,600 cpsi, greater than or equal to about 3,700cpsi, greater than or equal to about 3,800 cpsi, greater than or equalto about 3,900 cpsi, greater than or equal to about 4,000 cpsi, greaterthan or equal to about 4,100 cpsi, greater than or equal to about 4,200cpsi, greater than or equal to about 4,300 cpsi, greater than or equalto about 4,400 cpsi, greater than or equal to about 4,500 cpsi, greaterthan or equal to about 4,600 cpsi, greater than or equal to about 4,700cpsi, greater than or equal to about 4,800 cpsi, greater than or equalto about 4,900 cpsi, or greater than or equal to about 5,000 cpsi.Particularly, the substrate has a cell density greater than about 1,040cpsi and greater than or equal to about 1,400 cpsi. Additionally oralternatively, the substrate has a cell density of less than or equal toabout 900 cpsi, less than or equal to about 920 cpsi, less than or equalto about 940 cpsi, less than or equal to about 960 cpsi, less than orequal to about 980 cpsi, less than or equal to about 1,000 cpsi, lessthan or equal to about 1,020 cpsi, less than or equal to about 1,040cpsi, less than or equal to about 1,060 cpsi, less than or equal toabout 1,080 cpsi, less than or equal to about 1,100 cpsi, less than orequal to about 1,120 cpsi, less than or equal to about 1,140 cpsi, lessthan or equal to about 1,160 cpsi, less than or equal to about 1,180cpsi, less than or equal to about 1,200 cpsi, less than or equal toabout 1,220 cpsi, less than or equal to about 1,240 cpsi, less than orequal to about 1,260 cpsi, less than or equal to about 1,280 cpsi, lessthan or equal to about 1,300 cpsi, less than or equal to about 1,320cpsi, less than or equal to about 1,340 cpsi, less than or equal toabout 1,360 cpsi, less than or equal to about 1,380 cpsi, less than orequal to about 1,400 cpsi, less than or equal to about 1,420 cpsi, lessthan or equal to about 1,440 cpsi, less than or equal to about 1,460cpsi, less than or equal to about 1,480 cpsi, less than or equal toabout 1,500 cpsi, less than or equal to about 1,520 cpsi, less than orequal to about 1,640 cpsi, less than or equal to about 1,760 cpsi, lessthan or equal to about 1,880 cpsi, less than or equal to about 1,900cpsi, less than or equal to about 1,920 cpsi, less than or equal toabout 1,940 cpsi, less than or equal to about 1,960 cpsi, less than orequal to about 1,980 cpsi, less than or equal to about 2,000 cpsi, lessthan or equal to about 2,100 cpsi, less than or equal to about 2,200cpsi, less than or equal to about 2,300 cpsi, less than or equal toabout 2,400 cpsi, less than or equal to about 2,500 cpsi, less than orequal to about 2,600 cpsi, less than or equal to about 2,700 cpsi, lessthan or equal to about 2,800 cpsi, less than or equal to about 2,900cpsi, less than or equal to about 3,000 cpsi, less than or equal toabout 3,100 cpsi, less than or equal to about 3,200 cpsi, less than orequal to about 3,300 cpsi, less than or equal to about 3,400 cpsi, lessthan or equal to about 3,500 cpsi, less than or equal to about 3,600cpsi, less than or equal to about 3,700 cpsi, less than or equal toabout 3,800 cpsi, less than or equal to about 3,900 cpsi, less than orequal to about 4,000 cpsi, less than or equal to about 4,100 cpsi, lessthan or equal to about 4,200 cpsi, less than or equal to about 4,300cpsi, less than or equal to about 4,400 cpsi, less than or equal toabout 4,500 cpsi, less than or equal to about 4,600 cpsi, less than orequal to about 4,700 cpsi, less than or equal to about 4,800 cpsi, lessthan or equal to about 4,900 cpsi, or less than or equal to about 5,000cpsi. Ranges expressly disclosed include combinations of theabove-enumerated upper and lower limits, e.g., about 900 cpsi to about5,000 cpsi, about 1,500 cpsi to about 3,000 cpsi, about 1,500 cpsi toabout 4,000 cpsi, about 1,400 cpsi to about 3,300 cpsi, etc.Particularly, the substrate has a cell density of about 1,500 cpsi toabout 4,000 cpsi.

Exemplary channel geometries in the substrate include, but are notlimited to a trapezoidal geometry and a square geometry.

In various aspects, the substrate can be a porous solid. Exemplaryporous solids include, but are not limited to a metal oxide, amixed-metal oxide, a ceramic, a zeolite and combinations thereof. Metaloxides that can be used include, but are not limited to alumina, silica,zirconia and titania. An example of a suitable mixed-metal oxide ceramicincludes cordierite. Examples of suitable zeolites include, but are notlimited to ZSM-5 and ZSM-58.

In various aspects, the substrate has a porosity of less than or equalto about 40%, less than or equal to about 35%, less than or equal toabout 30%, less than or equal to about 25%, less than or equal to about20%, less than or equal to about 15%, less than or equal to about 10%,less than or equal to about 9%, less than or equal to about 8%, lessthan or equal to about 7%, less than or equal to about 6%, less than orequal to about 5%, less than or equal to about 4%, less than or equal toabout 3%, less than or equal to about 2%, less than or equal to about 1%or less than or equal to about 0.5%. Particularly, the substrate has aporosity of less than or equal to about 30%. Additionally oralternatively, the substrate has a porosity of greater than or equal toabout 40%, greater than or equal to about 35%, greater than or equal toabout 30%, greater than or equal to about 25%, greater than or equal toabout 20%, greater than or equal to about 15%, greater than or equal toabout 10%, greater than or equal to about 9%, greater than or equal toabout 8%, greater than or equal to about 7%, greater than or equal toabout 6%, greater than or equal to about 5%, greater than or equal toabout 4%, greater than or equal to about 3%, greater than or equal toabout 2%, greater than or equal to about 1% or greater than or equal toabout 0.5%. Ranges expressly disclosed include combinations of theabove-enumerated upper and lower limits, e.g., about 0.5% to about 40%,about 1% to about 10%, about 2% to about 30%, etc.

Additionally or alternatively, the substrate can be a non-porous solidhaving a porosity of about 0.0%. Exemplary non-porous solids include,but are not limited to a metal, a glass, and a plastic. The metal cancomprise stainless steel and/or aluminum.

B. Coating

In various aspects, the coating can comprise adsorbent particles. Theadsorbent particles can have an average diameter of greater than orequal to about 1 μm, greater than or equal to about 2 μm, greater thanor equal to about 4 μm, greater than or equal to about 6 μm, greaterthan or equal to about 8 μm, greater than or equal to about 10 μm,greater than or equal to about 12 μm, greater than or equal to about 14μm, greater than or equal to about 16 μm, greater than or equal to about18 μm, greater than or equal to about 20 μm, greater than or equal toabout 21 μm, greater than or equal to about 22 μm, greater than or equalto about 23 μm, greater than or equal to about 24 μm, greater than orequal to about 25 μm, greater than or equal to about 26 μm, greater thanor equal to about 27 μm, greater than or equal to about 28 μm, greaterthan or equal to about 29 μm, greater than or equal to about 30 μm,greater than or equal to about 32 μm, greater than or equal to about 34μm, greater than or equal to about 36 μm, greater than or equal to about38 μm, greater than or equal to about 40 μm, greater than or equal toabout 42 μm, greater than or equal to about 44 μm, greater than or equalto about 46 μm, greater than or equal to about 48 μm or greater than orequal to about 50 μm. Particularly, the adsorbent particles have anaverage diameter greater than about 20 μm. Additionally oralternatively, the adsorbent particles can have an average diameter ofless than or equal to about 1 μm, less than or equal to about 2 μm, lessthan or equal to about 4 μm, less than or equal to about 6 μm, less thanor equal to about 8 μm, less than or equal to about 10 μm, less than orequal to about 12 μm, less than or equal to about 14 μm, less than orequal to about 16 μm, less than or equal to about 18 μm, less than orequal to about 20 μm, less than or equal to about 21 μm, less than orequal to about 22 μm, less than or equal to about 23 μm, less than orequal to about 24 μm, less than or equal to about 25 μm, less than orequal to about 26 μm, less than or equal to about 27 μm, less than orequal to about 28 μm, less than or equal to about 29 μm, less than orequal to about 30 μm, less than or equal to about 32 μm, less than orequal to about 34 μm, less than or equal to about 36 μm, less than orequal to about 38 μm, less than or equal to about 40 μm, less than orequal to about 42 μm, less than or equal to about 44 μm, less than orequal to about 46 μm, less than or equal to about 48 μm or less than orequal to about 50 μm. Ranges expressly disclosed include combinations ofthe above-enumerated upper and lower limits, e.g., about 1 μm to about50 μm, about 2 μm to about 40 μm, about 10 μm to about 36 μm, etc.Particularly, the adsorbent particles can have an average diameter ofabout 2 μm to about 50 μm and/or about 20 μm to about 40 μm.

Additionally or alternatively, the adsorbent particles described hereincan generally have a hexagonal disc shape where the particles havehexagonal faces. The top and bottom hexagonal faces can generallycorrespond to larger hexagonal faces, with a smaller depth dimension(roughly) perpendicular to the top and bottom faces. The hexagonal discshape of the adsorbent particles can be seen in FIG. 8.

Additionally or alternatively, the adsorbent particles described hereincan generally have a rounded or circular disc shape with top and bottomrounded or circular disc faces. The depth dimension for the roundeddiscs can be smaller than the lateral dimension of the rounded faces ofthe disc.

One way to characterize the difference between the hexagonal disc shapeand the rounded disc shape can be based on the difference between thevertex-to-vertex distance and the edge-to-edge distance in a hexagonalface of a crystal. To perform this type of characterization, an initialstep can be to identify the correct face(s) of the particle forperforming the characterization. For a hexagonal disc particle, thecombination of a vertex-to-vertex line and an edge-to-edge line canroughly define a plane. The dimension perpendicular to this plane canthen correspond to the depth of the crystal. For the hexagonal discshape, this depth dimension can generally be shorter than either thevertex-to-vertex distance or the edge-to-edge distance. If the depthdistance is longer than either of the other two distances, then either adifferent hexagonal face should be selected for this calculation, or thecrystal may not correspond to a hexagonal disc shape or round discshape. After determining that the correct type of hexagonal (or rounded)face has been selected for characterizing the crystal, thevertex-to-vertex distance and the edge-to-edge distance for thehexagonal face can be compared in order to calculate an axis ratio.Additionally or alternatively, the adsorbent particles described hereincan be a prismatic shape.

FIG. 1 shows a schematic example of this type of calculation. In FIG. 1,line 110 corresponds to the vertex-to-vertex distance for a hexagon.Line 120 corresponds to the edge-to-edge distance. For a hexagonal facewith well defined edges and vertices, the vertex-to-vertex distance, bydefinition, is typically larger than the edge-to-edge distance. As theangles and edges of the hexagon become smoothed toward forming a circle,to the degree that the vertices and edges can still be identified, thevertex-to-vertex distance and the edge-to-edge distance can becomeincreasingly closer. In the limiting case of a circle, the axis ratio ofvertex-to-vertex distance and edge-to-edge distance becomes 1, with thecaveat that the location of a “vertex” and an “edge” in the limitingcase may be somewhat arbitrary.

For adsorbent particles of the type shown in FIG. 8, the ratio ofvertex-to-vertex distance versus edge-to-edge distance can be determinedbased on measuring distances in an SEM micrograph. The adsorbentparticles shown in FIG. 8 can be used herein in the coating and the axisratio of the vertex-to-vertex distance versus the edge-to-edge distancewas observed to be at least about 1.15, such as at least about 1.2.

The characterization of the rounded disc shape particles can beperformed in a similar manner. The depth dimension can be identified inrelation to the rounded (approaching circular) face(s) of the crystal.In some embodiments, a ratio of the depth dimension to the edge-to-edgedistance can be about 0.9 or less, e.g., about 0.85 or less. In suchembodiments, particles with a ratio of depth dimension to edge-to-edgedistance of greater than about 0.95 were identified to correspond to aroughly spherical morphology. The rounded face of the rounded discs canthen be characterized using the axis ratio. Additionally oralternatively, the round disc particles can have an axis ratio of thevertex-to-vertex distance versus edge-to-edge distance of about 1.1 orless, e.g., about 1.05 or less, or a still lower value that can approachthe limiting axis ratio value of 1.0.

Additionally or alternatively, the adsorbent particles comprise amicroporous material, such as a zeolite. The zeolite can have a Si/Alratio of at least about 200:1, at least about 300:1, at least about400:1, at least about 500:1, at least about 600:1, at least about 700:1,at least about 800:1, at least about 900:1 or at least about 1,000:1.Particularly, the zeolite can have a Si/Al ratio of about 600:1.Examples of suitable zeolites include, but are not limited to thefollowing zeolite frameworks: CDO, FAU, MFI, DOH, DDR and combinationsthereof. Particularly, the zeolite can be DDR. Examples of DDR frameworkzeolites include, but are not limited to Sigma-1, ZSM-58 and SSZ-28. Aperson of ordinary skill in the art knows how to make the aforementionedzeolites. For example, see the references provided in the InternationalZeolite Association's database of zeolite structures found atwww.iza-structure.org/databases. Particularly, the DDR framework zeolitecan be ZSM-58. For example, ZSM-58 can be formed according to themethods described in U.S. Patent Application Publication No.2014/0161717, the entirety of which is incorporated by reference.Additionally or alternatively, the DDR framework zeolite can include DDRframeworks formed according to the methods described in U.S. ProvisionalPatent Application Ser. No. 62/082,210, the entirety of which isincorporated by reference.

Additionally or alternatively, the coating can also comprise a binder.The binder particles are capable of binding the adsorbent particlestogether to form an aggregate of binder particles and adsorbentparticles in the coating. The binder can comprise particles having anaverage diameter of greater than or equal to about 10 nm, greater thanor equal to about 15 nm, greater than or equal to about 20 nm, greaterthan or equal to about 25 nm, greater than or equal to about 30 nm,greater than or equal to about 35 nm, greater than or equal to about 45nm, greater than or equal to about 50 nm, greater than or equal to about55 nm, greater than or equal to about 60 nm, greater than or equal toabout 65 nm, greater than or equal to about 70 nm, greater than or equalto about 75 nm, greater than or equal to about 80 nm, greater than orequal to about 85 nm, greater than or equal to about 90 nm, greater thanor equal to about 95 nm, greater than or equal to about 100 nm, greaterthan or equal to about 110 nm, greater than or equal to about 120 nm,greater than or equal to about 130 nm, greater than or equal to about140 nm, greater than or equal to about 150 nm, greater than or equal toabout 160 nm, greater than or equal to about 170 nm, greater than orequal to about 180 nm, greater than or equal to about 190 nm, greaterthan or equal to about 200 nm, greater than or equal to about 210 nm,greater than or equal to about 220 nm, greater than or equal to about230 nm, greater than or equal to about 240 nm or greater than or equalto about 250 nm. Additionally or alternatively, the binder can compriseparticles can have an average diameter of less than or equal to about 10nm, less than or equal to about 15 nm, less than or equal to about 20nm, less than or equal to about 25 nm, less than or equal to about 30nm, less than or equal to about 35 nm, less than or equal to about 45nm, less than or equal to about 50 nm, less than or equal to about 55nm, less than or equal to about 60 nm, less than or equal to about 65nm, less than or equal to about 70 nm, less than or equal to about 75nm, less than or equal to about 80 nm, less than or equal to about 85nm, less than or equal to about 90 nm, less than or equal to about 95nm, less than or equal to about 100 nm, less than or equal to about 110nm, less than or equal to about 120 nm, less than or equal to about 130nm, less than or equal to about 140 nm, less than or equal to about 150nm, less than or equal to about 160 nm, less than or equal to about 170nm, less than or equal to about 180 nm, less than or equal to about 190nm, less than or equal to about 200 nm, less than or equal to about 210nm, less than or equal to about 220 nm, less than or equal to about 230nm, less than or equal to about 240 nm or less than or equal to about250 nm. Ranges expressly disclosed include combinations of theabove-enumerated upper and lower limits, e.g., about 10 nm to about 250nm, about 25 nm to about 200 nm, about 100 nm to about 200 nm, etc.Particularly, the binder particles can have an average diameter of about100 nm to about 200 nm.

Additionally or alternatively, the binder is basic. The binder can havea pH of greater than or equal to about 7, greater than or equal to about7.5, greater than or equal to about 8, greater than or equal to about8.5, greater than or equal to about 9, greater than or equal to about9.5, greater than or equal to about 10, greater than or equal to about10.5, greater than or equal to about 11, greater than or equal to about11.5, greater than or equal to about 12, greater than or equal to about12.5, greater than or equal to about 13, greater than or equal to about13.5 or greater than or equal to about 14. Particularly, the binder canhave a pH greater than about 7, particularly about 10. Additionally oralternatively, the binder has a pH of less than or equal to about 7,less than or equal to about 7.5, less than or equal to about 8, lessthan or equal to about 8.5, less than or equal to about 9, less than orequal to about 9.5, less than or equal to about 10, less than or equalto about 10.5, less than or equal to about 11, less than or equal toabout 11.5, less than or equal to about 12, less than or equal to about12.5, less than or equal to about 13, less than or equal to about 13.5or less than or equal to about 14. Ranges expressly disclosed includecombinations of the above-enumerated upper and lower limits, e.g., about7 to about 14, about 10 to about 12, about 11 to about 13.5, about 11 toabout 12.5, etc. Particularly, the pH can be from about 7 to about 11.

Exemplary materials suitable for use as the binder include but are notlimited to silica (SiO₂) and alumina (Al₂O₃). Particularly, the bindercan comprise SiO₂.

Additionally or alternatively, the coating can be present on thesubstrate in a thickness of greater than or equal to about 20 μm,greater than or equal to about 30 μm, greater than or equal to about 40μm, greater than or equal to about 50 μm, greater than or equal to about60 μm, greater than or equal to about 70 μm, greater than or equal toabout 80 μm, greater than or equal to about 90 μm, greater than or equalto about 100 μm, greater than or equal to about 110 μm, greater than orequal to about 120 μm, greater than or equal to about 130 μm, greaterthan or equal to about 140 μm, greater than or equal to about 150 μm,greater than or equal to about 160 μm, greater than or equal to about170 μm, greater than or equal to about 180 μm, greater than or equal toabout 190 μm, greater than or equal to about 200 μm, greater than orequal to about 210 μm, greater than or equal to about 220 μm, greaterthan or equal to about 230 μm, greater than or equal to about 240 μm,greater than or equal to about 250 μm, greater than or equal to about260 μm, greater than or equal to about 270 μm, greater than or equal toabout 280 μm, greater than or equal to about 290 μm, or greater than orequal to about 300 μm. Particularly, the coating can be present on thesubstrate in a thickness of greater than or equal to about 100 μm.Additionally or alternatively, the coating can be present on thesubstrate in a thickness of less than or equal to about 20 μm, less thanor equal to about 30 μm, less than or equal to about 40 μm, less than orequal to about 50 μm, less than or equal to about 60 μm, less than orequal to about 70 μm, less than or equal to about 80 μm, less than orequal to about 90 μm, less than or equal to about 100 μm, less than orequal to about 110 μm, less than or equal to about 120 μm, less than orequal to about 130 μm, less than or equal to about 140 μm, less than orequal to about 150 μm, less than or equal to about 160 μm, less than orequal to about 170 μm, less than or equal to about 180 μm, less than orequal to about 190 μm, less than or equal to about 200 μm, less than orequal to about 210 μm, less than or equal to about 220 μm, less than orequal to about 230 μm, less than or equal to about 240 μm, less than orequal to about 250 μm, less than or equal to about 260 μm, less than orequal to about 270 μm, less than or equal to about 280 μm, less than orequal to about 290 μm, or less than or equal to about 300 μm. Rangesexpressly disclosed include combinations of the above-enumerated upperand lower limits, e.g., about 20 μm to about 300 μm, about 30 μm toabout 200 μm, about 50 μm to about 100 μm, etc. Particularly, thecoating on the substrate can have a thickness of about 30 μm to about200 μm.

Additionally or alternatively, the coating can comprise one or morelayers of adsorbent particles and binder particles. The coating cancomprise two or more layers, three or more layers, four or more layers,five or more layers, six or more layers, seven or more layers, eight ormore layers, nine or more layers, or ten or more layers of adsorbentparticles and binder particles. Additionally or alternatively, thecoating can comprise two or fewer layers, three or fewer layers, four orfewer layers, five or fewer layers, six or fewer layers, seven or fewerlayers, eight or fewer layers, nine or fewer layers, or ten or fewerlayers of adsorbent particles and binder particles. Ranges expresslydisclosed include combinations of the above-enumerated upper and lowerlimits, e.g., one to ten layers, two to eight layers, three to sevenlayers, etc.

Additionally or alternatively, the coating on the substrate can have amacroporosity of at least about 5%, at least about 10%, at least about15%, at least about 20%, at least about 25%, at least about 30%, atleast about 35%, at least about 40%, at least about 45% or at leastabout 50%. The coating on the substrate can have a macroporosity of lessthan about 5%, less than about 10%, less than about 15%, less than about20%, less than about 25%, less than about 30%, less than about 35%, lessthan about 40%, less than about 45% or less than about 50%. Rangesexpressly disclosed include combinations of the above-enumerated upperand lower limits, e.g., about 5% to about 50%, about 10% to about 40%,about 20% to about 35%, etc. Particularly, the coating on the substratecan have a macroporosity of about 10% to about 40%.

C. Primer Layer

Additionally or alternatively, the adsorbent bed may further comprise aprimer layer on the substrate. The primer layer can be present betweenthe substrate and the coating. The primer layer can increase surfaceroughness of the substrate and/or provide a surface more similar incomposition to the adsorbent particles in the coating for increasedadhesion and improved bonding of the coating to the substrate.Additionally, when the substrate is a metal, the primer layer can reduceexposure of potentially reactive species on the metal surface and alsodiminish thermal expansion differences between the metal surface and thecoating. The primer layer can be a zirconium-containing layer.Particularly, the zirconium-containing layer can comprise zirconiumoxide, zirconium silicate or a combination thereof.

III. Methods of Preparing the Structured Adsorbent Bed

In various aspects, a method of preparing a structured adsorbent beddescribed herein is provided. The method can comprise pretreating thesubstrate, preparing an aqueous slurry comprising the adsorbentparticles and the binder and applying the aqueous slurry to thesubstrate to form the coating on the substrate.

Additionally or alternatively, pretreating the substrate can compriseapplying a primer layer, such as the zirconium-containing layerdescribed herein. Additionally or alternatively, the substrate can becleaned prior to application of the primer layer.

Additionally or alternatively, pretreating the substrate can compriseheating the substrate and applying a primer layer, such as thezirconium-containing layer described herein. When the substrate is ametal having no porosity, heating the substrate prior to application ofthe primer layer results in a micron-thin metal oxide skin, whichroughens the metal surface and creates anchoring sites on the metalsurface thereby improving adhesion and bonding of the coating. Inpretreating the substrate, the substrate can be heated at a temperatureof greater than or equal to about 500° C., greater than or equal toabout 550° C., greater than or equal to about 600° C., greater than orequal to about 650° C., greater than or equal to about 700° C., greaterthan or equal to about 750° C., greater than or equal to about 800° C.,greater than or equal to about 850° C., greater than or equal to about900° C., greater than or equal to about 950° C., greater than or equalto about 1,000° C., greater than or equal to about 1,050° C., greaterthan or equal to about 1,100° C., greater than or equal to about 1,150°C., greater than or equal to about 1,200° C., greater than or equal toabout 1,250° C., or greater than or equal to about 1,300° C.Additionally or alternatively, the substrate can be heated at atemperature of less than or equal to about 500° C., less than or equalto about 550° C., less than or equal to about 600° C., less than orequal to about 650° C., less than or equal to about 700° C., less thanor equal to about 750° C., less than or equal to about 800° C., lessthan or equal to about 850° C., less than or equal to about 900° C.,less than or equal to about 950° C., less than or equal to about 1,000°C., less than or equal to about 1,050° C., less than or equal to about1,100° C., less than or equal to about 1,150° C., less than or equal toabout 1,200° C., less than or equal to about 1,250° C., or less than orequal to about 1,300° C. Ranges expressly disclosed include combinationsof the above-enumerated upper and lower limits, e.g., about 500° C. toabout 1,300° C., about 600° C. to about 1,100° C., about 900° C. toabout 1050° C., etc. The substrate can be heated at a temperature ofabout 600° C. to about 1,100° C., particularly about 900° C.

Additionally or alternatively, the substrate can be pre-treated byheating the substrate for at least about 1 hour, at least about 2 hours,at least about 3 hours, at least about 4 hours, at least about 5 hours,at least about 6 hours, at least about 7 hours, at least about 8 hours,at least about 9 hours or at least about 10 hours, particularly at leastabout 6 hours. Alternatively or additionally, the substrate can beheated for less than about 1 hour, less than about 2 hours, less thanabout 3 hours, less than about 4 hours, less than about 5 hours, lessthan about 6 hours, less than about 7 hours, less than about 8 hours,less than about 9 hours or less than about 10 hours. Ranges expresslydisclosed include combinations of the above-enumerated upper and lowerlimits, e.g., about 1 hour to about 10 hours, about 1 hour to about 2hours, about 2 hours to about 6 hours, etc.

Additionally or alternatively, the aqueous slurry can comprise theadsorbent particles and the binder, both as described herein, in aweight ratio from about 70:30 w/w to about 90:10 w/w. Particularly, theweight ratio of adsorbent particles to binder in the aqueous slurry canbe about 80:20 w/w or about 90:10 w/w. Particularly, the binder in theaqueous slurry can be SiO₂. Additionally or alternatively, the aqueousslurry can include viscosity modifiers, water and/or dispersants.

Coating adhesion, particle cohesion and uniformity depend on slurryproperties. Further, the size of the suspended particles has a greatinfluence on the stability of the suspension and adhesion to thesubstrate. In one aspect, the adsorbent particles in the slurry have anaverage diameter of greater than or equal to about 25 μm. Additionallyor alternatively, the binder particles in the slurry have an averagediameter of from about 100 nm to about 200 nm. The aqueous slurry asdescribed herein can be stable for many hours, for example about 5,about 10, about 15, about 20, about 25, about 30 hours if stirred andminutes if not stirred. Further, the aqueous slurry can have a pH ofabout 7 to about 10 and an approximate viscosity of 14.4 cP.Additionally or alternatively, the aqueous slurry can also includeorganic additives for controlling rheology of the slurry and/or to actas temporary binding aids.

Additionally or alternatively, the aqueous slurry can be applied to thesubstrate by dip coating techniques, pulling the slurry into thesubstrate with a vacuum and/or pumping the slurry into the substrate.Multiple coatings of the aqueous slurry can be applied to the substrate,for example, at least one coating, at least two coatings, at least threecoatings, at least four coatings, at least five coatings, at least sixcoatings, at least seven coatings, at least eight coatings, at leastnine coatings or at least ten coatings.

Additionally or alternatively, the method further comprises removingexcess coating from the coated substrate, drying the coated substrateand/or heating the coated substrate.

Removing the excess coating in a high cell density substrate (e.g.,monoliths) can be difficult due to the high capillary forces within thecells as result of the smaller channel diameter (e.g., 400 μm) of thehigh cell density substrates. To remove excess coating from the channelsin the substrate, the pressure drop across the substrate must be greaterthan the capillary force through the channel. Thus, in one aspect, theexcess coating can be removed from the substrate by flowing a gas, suchas nitrogen, through the coated substrate at a rate greater than orequal to about 100 L/min, greater than or equal to about 150 L/min,greater than or equal to about 200 L/min, or greater than or equal toabout 250 L/min. Particularly, the gas can be flowed through thesubstrate at a rate greater than or equal to about 100 L/min.Additionally or alternatively, the gas can be flowed through thesubstrate at a rate lesser than or equal to about 100 L/min, lesser thanor equal to about 150 L/min, lesser than or equal to about 200 L/min, orlesser than or equal to about 250 L/min. Ranges expressly disclosedinclude combinations of the above-enumerated upper and lower limits,e.g., about 100 L/min to about 250 L/min, about 100 L/min to about 200L/min, etc.

Additionally or alternatively, drying the coated substrate can compriseflash drying the coated substrate. The gas flowed through the substrateat a high flow rate to remove excess coating can result in rapidevaporative cooling of the slurry in the channels. This can lead toslower water evaporation and drying of the slurry, which can contributeto “bridging,” resulting in channels being blocked by unstable, mobileslurry particles bridging the cell diameter in the monoliths and dryinginto plugs. Flash drying the coated substrate may stabilize the coatingfilms and prevent “bridging” and size segregation of the zeolite andbinder particles upon vertical standing. The flash drying can compriseheating a gas purge, such as the same gas used to remove the excesscoating, to about 40° C., about 45° C., about 50° C., about 55° C.,about 60° C., about 65° C. or about 70° C., particularly between about50° C. and about 60° C. The heated gas purge can be flowed through thecoated substrate at a rate of at least about 100 L/min, at least about150 L/min, at least about 200 L/min, or at least about 250 L/min.Particularly, the heated purge gas can be flowed through the substrateat a rate of at least about 100 L/min. Additionally or alternatively,the heated gas purge can be flowed through the coated substrate at arate of no greater than about 100 L/min, no greater than about 150L/min, no greater than about 200 L/min, or no greater than about 250L/min. Ranges expressly disclosed include combinations of theabove-enumerated upper and lower limits, e.g., about 100 L/min to about250 L/min, about 100 L/min to about 200 L/min, etc.

Additionally or alternatively, the method further comprises calciningthe coated substrate, which optionally, can be performed after thecoated substrate is dried. The calcining can be performed in air. Thecalcining can be performed at a temperature suitable for degradingand/or removing substantially all of the volatile organic components andwater in the structured adsorbent bed, for example, at least about 300°C., at least about 350° C., at least about 400° C., at least about 450°C., about 500° C., at least about 550° C. or at least about 600° C.Additionally or alternatively, the calcining can be performed at atemperature of less than about 300° C., less than about 350° C., lessthan about 400° C., less than about 450° C., less than about 500° C.,less than about 550° C. or less than about 600° C. Ranges expresslydisclosed include combinations of the above-enumerated upper and lowerlimits, e.g., about 300° C. to about 600° C., about 350° C. to about450° C., about 300° C. to about 500° C., etc. Particularly, thecalcining is performed at a temperature of about 500° C., optionallyusing a heating ramp, such as: a) drying at about 120° C. for about 8hours; b) increasing the temperature to about 500° C. over about 4hours; c) holding at about 500° C. for about 2 hours; and d) cooling toabout 120° C. over about 2 hours.

IV. Gas Separation Processes

In various aspects, a gas separation process is provided herein. The gasseparation process comprises contacting a gas mixture containing atleast one contaminant with a structured adsorbent bed as describedherein.

In various aspects, the gas separation process can be achieved by swingadsorption processes, such as pressure swing adsorption (PSA) andtemperature swing adsorption (TSA). All swing adsorption processes havean adsorption step in which a feed mixture (typically in the gas phase)is flowed over an adsorbent that preferentially adsorbs a more readilyadsorbed component relative to a less readily adsorbed component. Acomponent may be more readily adsorbed because of kinetic or equilibriumproperties of the adsorbent. The adsorbent can typically be contained ina contactor that is part of the swing adsorption unit. The contactor cantypically contain an engineered structured adsorbent bed or aparticulate adsorbent bed. The bed can contain the adsorbent and othermaterials such as other adsorbents, mesopore filling materials, and/orinert materials used to mitigate temperature excursions from the heat ofadsorption and desorption. Other components in the swing adsorption unitcan include, but are not necessarily limited to, valves, piping, tanks,and other contactors.

PSA processes rely on the fact that gases under pressure tend to beadsorbed within the pore structure of the adsorbent materials.Typically, the higher the pressure, the greater the amount of targetedgas component that will be adsorbed. When the pressure is reduced, theadsorbed targeted component is typically released, or desorbed. PSAprocesses can be used to separate gases of a gas mixture, becausedifferent gases tend to fill the pores or free volume of the adsorbentto different extents due to either the equilibrium or kinetic propertiesof the adsorbent. In many important applications, to be described as“equilibrium-controlled” processes, the adsorptive selectivity isprimarily based upon differential equilibrium uptake of the first andsecond components. In another important class of applications, to bedescribed as “kinetic-controlled” processes, the adsorptive selectivityis primarily based upon the differential rates of uptake of the firstand second components.

If a gas mixture, such as natural gas, is passed under pressure througha vessel containing a polymeric or microporous adsorbent that is moreselective towards carbon dioxide than it is for methane, at least aportion of the carbon dioxide can be selectively adsorbed by theadsorbent, and the gas exiting the vessel can be enriched in methane.When the adsorbent reaches the end of its capacity to adsorb carbondioxide, it can be regenerated by reducing the pressure, therebyreleasing the adsorbed carbon dioxide. The adsorbent can then typicallypurged and repressurized and ready for another adsorption cycle.

TSA processes also rely on the fact that gases under pressure tend to beadsorbed within the pore structure of the adsorbent materials. When thetemperature of the adsorbent is increased, the adsorbed gas is typicallyreleased, or desorbed. By cyclically swinging the temperature ofadsorbent beds, TSA processes can be used to separate gases in a mixturewhen used with an adsorbent selective for one or more of the componentsin a gas mixture. Partial pressure purge displacement (PPSA) swingadsorption processes regenerate the adsorbent with a purge. Rapid cycle(RC) swing adsorption processes complete the adsorption step of a swingadsorption process in a short amount of time. For kinetically selectiveadsorbents, it can be preferable to use a rapid cycle swing adsorptionprocess. If the cycle time becomes too long, the kinetic selectivity canbe lost. These swing adsorption protocols can be performed separately orin combinations. Examples of processes that can be used herein eitherseparately or in combination are PSA, TSA, pressure temperature swingadsorption (PTSA), partial purge displacement swing adsorption (PPSA),PPTSA, rapid cycle PSA (RCPSA), RCTSA, vacuum pressure swing adsorption(VPSA), RCPPSA and RCPTSA.

In PSA processes, a feed gas mixture containing the first and second gascomponents is separated by cyclic variations of pressure coordinatedwith cyclic reversals of flow direction in a flow path contacting afixed bed of the adsorbent material in an adsorber vessel. In the caseof TSA or PPSA processes, cyclic variations of temperature and/orpartial pressure of the gas components may be coordinated with gas flowthrough a flow path to perform a separation. The process in any specificPSA application operates at a cyclic frequency characterized by itsperiod, and over a pressure envelope between a first relatively higherpressure and a second relatively lower pressure. Separation in PSA isachieved by coordinating the pressure variations with the flow patternwithin the flow path, so that the gas mixture in the flow path isenriched in the second component (owing to preferential adsorptiveuptake of the first component in the adsorbent material) when flowing ina first direction in the flow path, while the gas mixture is enriched inthe first component (which has been desorbed by the adsorbent material)when flowing in the opposite direction in the flow path. In order toachieve separation performance objectives (i.e. product gas purity,recovery and productivity), process parameters and operating conditionsshould be designed to achieve a sufficiently high adsorptive selectivityof the first and second components over the adsorbent material, at thecyclic frequency and within the pressure envelope.

Swing adsorption processes can be applied to remove a variety of targetgases, also referred to as a “contaminant gas” from a wide variety ofgas mixtures. The “light component” as utilized herein is taken to bethe species or molecular component(s) not preferentially taken up by theadsorbent in the adsorption step of the process. Conversely, the “heavycomponent” as utilized herein is taken to be the species or molecularcomponent(s) preferentially taken up by the adsorbent in the adsorptionstep of the process.

An example of a gas mixture that can be separated in the methodsdescribed herein is a gas mixture comprising CH₄, such as a natural gasstream. A gas mixture comprising CH₄ can contain significant levels ofcontaminants such as H₂O, H₂S, CO₂, N₂, mercaptans, and/or heavyhydrocarbons. Additionally or alternatively, the gas mixture cancomprise NO_(x) and/or SO_(x) species as contaminants, such as a wastegas stream, a flue gas stream and a wet gas stream. As used herein, theterms “NO_(x)” and “NO_(x) species” refers to the various oxides ofnitrogen that may be present in waste gas, such as waste gas fromcombustion processes. The terms refer to all of the various oxides ofnitrogen including, but not limited to, nitric oxide (NO), nitrogendioxide (NO₂), nitrogen peroxide (N₂O), nitrogen pentoxide (N₂O₅), andmixtures thereof. As used herein, the terms “SO_(x)” and “SOx species”refers to various oxides of sulfur that may be present in waste gas,such as waste gas from combustion processes. The terms refer to all ofthe various oxides of sulfur including, but not limited to, SO, SO₂,SO₃, SO₄, S₇O₂ and S₆O₂. Thus, examples of contaminants include, but arenot limited to H₂O, H₂S, CO₂, N₂, mercaptans, heavy hydrocarbons, NO_(x)and/or SO_(x) species.

In the practice of the present invention, it may be desirable to operatewith a multiplicity of structured adsorbent beds, with several coupledin a heating/cooling operation and others involved in adsorption (and/ordesorption). In such an operation, the adsorbent bed can besubstantially cooled by a circulating heat transfer medium before it isswitched into service for adsorption. One advantage of such an operationcan be that the thermal energy used to swing the bed is retained in theheat transfer medium. If adsorption were to proceed simultaneously withcooling, then a substantial part of the heat in the bed could be lost tothe adsorbate-free feed, and a higher heat load could be needed torestore the high temperature of the heat transfer medium.

Adsorptive kinetic separation (AKS) processes, as described above, areuseful for development and production of hydrocarbons, such as gas andoil processing. Particularly, as described in U.S. Patent ApplicationPublication No. 2013/032716, which is herein incorporated by referencein its entirety, the AKS processes described herein can use one or morekinetic swing adsorption process, such as pressure swing adsorption(PSA), thermal swing adsorption (TSA), calcination, and partial pressureswing or displacement purge adsorption (PPSA), including combinations ofthese processes; each swing adsorption process may be utilized withrapid cycles, such as using one or more rapid cycle pressure swingadsorption (RC-PSA) units, with one or more rapid cycle temperatureswing adsorption (RC-TSA) units or with one or more rapid cycle partialpressure swing adsorption (RC-PPSA) units; exemplary kinetic swingadsorption processes are described in U.S. Pat. Nos. 7,959,720;8,545,602; 8,529,663; 8,444,750; and 8,529,662 and U.S. ProvisionalApplication Nos. 61/448,121; 61/447,848; 61/447,869; and 61/447,877,which are each herein incorporated by reference in its entirety. Theprovided processes, can be useful for rapid, large scale, efficientseparation of a variety of target gases from gas mixtures.

The provided processes and apparatuses may be used to prepare naturalgas products by removing contaminants. The provided processes andapparatuses can be useful for preparing gaseous feed streams for use inutilities, including separation applications such as dew point control,sweetening/detoxification, corrosion protection/control, dehydration,heating value, conditioning, and purification. Examples of utilitiesthat utilize one or more separation applications can include generationof fuel gas, seal gas, non-potable water, blanket gas, instrument andcontrol gas, refrigerant, inert gas, and hydrocarbon recovery. Exemplary“not to exceed” product (or “target”) acid gas removal specificationscan include: (a) 2 vol % CO₂, 4 ppm H₂S; (b) 50 ppm CO₂, 4 ppm H₂S; or(c) 1.5 vol % CO₂, 2 ppm H₂S.

The provided processes and apparatuses may also be used to remove acidgas from hydrocarbon streams. Acid gas removal technology becomesincreasingly important as remaining gas reserves exhibit higherconcentrations of acid (sour) gas resources. Hydrocarbon feed streamscan vary widely in amount of acid gas, such as from several parts permillion to 90 vol %. Non-limiting examples of acid gas concentrationsfrom exemplary gas reserves can include concentrations of at least: (a)1 vol % H₂S, 5 vol % CO₂; (b) 1 vol % H₂S, 15 vol % CO₂; (c) 1 vol %H₂S, 60 vol % CO₂; (d) 15 vol % H₂S, 15 vol % CO₂; or (e) 15 vol % H₂S,30 vol % CO₂.

One or more of the following may be utilized with the processes andapparatuses provided herein, to prepare a desirable product stream,while maintaining relatively high hydrocarbon recovery:

(a) removing acid gas with RC-TSA using advanced cycles and purges asdescribed in U.S. Provisional Application No. 61/447,854, filed Mar. 1,2011, as well as the U.S. Pat. No. 8,784,533, which are togetherincorporated by reference herein in their entirety;

(b) using a mesopore filler to reduce the amount of trapped methane inthe adsorbent bed and increase the overall hydrocarbon recovery, asdescribed in U.S. Pat. Nos. 7,959,720; 8,444,750; and 8,529,663, each ofwhich is herein incorporated by reference in its entirety;

(c) depressurizing one or more RC-TSA units in multiple steps tointermediate pressures so that the acid gas exhaust can be captured at ahigher average pressure, thereby decreasing the compression required foracid gas injection; pressure levels for the intermediatedepressurization steps may be matched to the interstage pressures of theacid gas compressor to optimize the overall compression system;

(d) using exhaust or recycle streams to minimize processing andhydrocarbon losses, such as using exhaust streams from one or moreRC-TSA units as fuel gas instead of re-injecting or venting;

(e) using multiple adsorbent particles in a single bed to remove traceamounts of first contaminants, such as H₂S, before removal of a secondcontaminant, such as CO₂; such segmented beds may provide rigorous acidgas removal down to ppm levels with RC-TSA units with minimal purge flowrates;

(f) using feed compression before one or more RC-TSA units to achieve adesired product purity;

(g) contemporaneous removal of non-acid gas contaminants such asmercaptans, COS, and BTEX; selection processes and materials toaccomplish the same;

(h) selecting a cycle time and cycle steps based on adsorbent materialkinetics; and

(i) using a process and apparatus that uses, among other equipment, twoRC-TSA units in series, wherein the first RC-TSA unit cleans a feedstream down to a desired product purity and the second RC-TSA unitcleans the exhaust from the first unit to capture methane and maintainhigh hydrocarbon recovery; use of this series design may reduce the needfor a mesopore filler.

The processes, apparatuses, and systems provided herein can be useful inlarge gas treating facilities, such as facilities that process more thanfive million standard cubic feet per day (MSCFD) of natural gas, forexample more than 15 MSCFD, more than 25 MSCFD, more than 50 MSCFD, morethan 100 MSCFD, more than 500 MSCFD, more than one billion standardcubic feet per day (BSCFD), or more than two BSCFD.

V. Further Embodiments

The invention can additionally or alternately include one or more of thefollowing embodiments.

Embodiment 1

A structured adsorbent bed for purification of a gas feedstreamcomprising: a substrate having a cell density greater than 1040 cpsi;and a coating on the substrate, wherein the coating comprises adsorbentparticles and a binder.

Embodiment 2

The structured adsorbent bed of embodiment 1, wherein the adsorbentparticles have an average diameter of about 2 μm to about 40 μm.

Embodiment 3

The structured adsorbent bed of embodiment 1, wherein the adsorbentparticles have an average diameter greater than about 20

Embodiment 4

The structured adsorbent bed of any of the previous embodiments, whereinthe adsorbent particles have an axis ratio of at least 1.2.

Embodiment 5

The structured adsorbent bed of any of the previous embodiments, whereinthe adsorbent particles comprise a microporous material.

Embodiment 6

The structured adsorbent bed of embodiment 5, wherein the microporousmaterial comprises a zeolite, such as DDR (e.g., Sigma-1 and ZSM-58).

Embodiment 7

The structured adsorbent bed of any of the previous embodiments, whereinthe binder comprises particles having an average diameter of about 25 nmto about 200 nm, particularly 100 nm to about 200 nm.

Embodiment 8

The structured adsorbent bed of any of the previous embodiments, whereinthe binder has a pH greater than 7.

Embodiment 9

The structured adsorbent bed of any of the previous embodiments, whereinthe binder comprises SiO₂.

Embodiment 10

The structured adsorbent bed of any of the previous embodiments, whereinthe substrate has a cell density of about 1400 cpsi or greater.

Embodiment 11

The structured adsorbent bed of any of the previous embodiments, whereinthe substrate has a cell density of about 1500 cpsi to about 4000 cpsi.

Embodiment 12

The structured adsorbent bed of any of the previous embodiments, whereinthe coating on the substrate has a thickness of at least 100 μm orgreater.

Embodiment 13

The structured adsorbent bed of embodiment 1, wherein the coating on thesubstrate has a thickness of about 30 μm to about 200 μm.

Embodiment 14

The structured adsorbent bed of any of the previous embodiments, whereinthe substrate is a porous solid selected from the group consisting of ametal oxide, a mixed-metal oxide, a ceramic and a zeolite and/or has aporosity of about 30% or less, or alternatively the substrate is anon-porous solid selected from the group consisting of a metal (e.g.,stainless steel), a glass and a plastic.

Embodiment 15

The structured adsorbent bed of any of the previous embodiments furthercomprising a zirconium-containing layer (e.g., zirconium oxide,zirconium silicate and/or a combination thereof).

Embodiment 16

A method of preparing the structured adsorbent bed of any of theprevious embodiments, the method comprising: pretreating the substrate;and/or preparing an aqueous slurry comprising the adsorbent particlesand the binder; and/or applying the aqueous slurry to the substrate toform the coating on the substrate.

Embodiment 17

The method of embodiment 16, wherein pretreating the substratecomprises: (i) applying the zirconium-containing layer (e.g., zirconiumoxide, zirconium silicate and/or a combination thereof) to thesubstrate; or (ii) heating the substrate, particularly at about 600° C.to about 1100° C., and applying the zirconium-containing layer to thesubstrate.

Embodiment 18

The method of embodiment 16 or 17, wherein the binder is SiO₂.

Embodiment 19

The method of embodiment 16, 17, or 18 wherein the weight ratio of theadsorbent particles to the binder is from about 70:30 w/w to about 90:10w/w.

Embodiment 20

The method of embodiment 16, 17, 18, or 19 further comprising: removingexcess coating from the coated substrate; and/or drying the coatedsubstrate; and/or heating the coated substrate.

Embodiment 21

The method of embodiment 20, wherein the excess coating is removed fromthe substrate by flowing a gas through the coated substrate at a rateequal to or greater than about 100 L/min.

Embodiment 22

The method of embodiment 20, wherein drying the coated substratecomprises flash drying the coated substrate wherein a gas purge heatedfrom about 50° C. to about 60° C. is flowed through the coated substrateat rate of at least 100 L/min.

Embodiment 23

The method of embodiments 16, 17, 18, 19, 20, 21, or 22 wherein thecoating has about 10% to about 40% macroporosity.

Embodiment 24

A gas separation process comprising contacting a gas mixture containingat least one contaminant with the structured adsorbent bed ofembodiments 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15.

Embodiment 25

The gas separation process of embodiment 24, wherein the gas mixturecomprises CH₄ and/or the at least one contaminant is selected from thegroup consisting CO₂, H₂O, H₂S, NO_(x) and SO_(x).

Embodiment 26

The gas separation process of embodiment 24 or 25, wherein the processcomprises PSA, TSA, PPSA, PTSA, RCPSA, RCTSA, RCPPSA or RCPTSA.

Examples

The following examples are merely illustrative, and do not limit thisdisclosure in any way.

Example 1—Synthesis 1. Materials Substrates

High cell density metal and ceramic substrates were obtained as follows:

-   -   Spiral-wound 316 stainless steel monoliths were obtained from        Catacel Corporation. The metal monoliths were ˜6 inches long and        had diameters of ˜1.1 inches. Cell densities of the metal        monoliths included ˜1440 cpsi and ˜2918 cpsi. The monoliths were        a corrugated foil matrix which consisted of flat-on-corrugated        sheets that were wound around a central pin. The structures were        brazed and tack welded for mechanical strength. The individual        cells within the monolith had a trapezoidal geometry. The cell        dimensions of the ˜1440 cpsi monoliths were approximately 0.55        mm×0.55 mm. The cell dimensions of the ˜2918 cpsi monoliths were        approximately 0.38×0.42 mm.    -   Very low porosity ceramic monoliths (<6% wall porosity)        consisting of pure Al₂O₃ were obtained from Applied Ceramics        Company. The ceramic monoliths were ˜6 inches long with        diameters of ˜1.1 inches. The cell densities of the ceramic        monoliths included ˜1500 cpsi and ˜2700 cpsi. The individual        cells had a square geometry. The cell dimensions of the ˜1500        cpsi monoliths were approximately 0.55 mm×0.55 mm. The cell        dimensions of the ˜2700 cpsi monoliths were approximately        0.40×0.40 mm. Scanning electron microscope (SEM) images of the        ˜2700 cpsi ceramic monolith is shown in FIGS. 2a and 2 b.

Adsorbent Materials:

DDR zeolites prepared according to the methods described in U.S. PatentApplication Publication No. 2014/0161717 with a Si/Al ratio of ˜600:1and a SiO₂/Al₂O₃ ratio of ˜300:1 were used in the coating formulations.The particle sizes of the DDR zeolites were very large, with the averageparticle diameter in the range of ˜25 μm to ˜30 μm.

2. Pre-Treatment of Substrate

Two pre-treatment options were used:

-   -   (i) A Zr-based primer layer was applied as a first layer to the        metal and the ceramic monoliths. The metal structures were first        cleaned with a phosphate solution (i.e., ˜1% trisodium phosphate        solution) to remove any processing oils. The ceramic structures        were pre-cleaned with acetone, ethanol and water separately to        remove any processing materials; or    -   (ii) A high temperature thermal oxidation treatment was        performed on the metal monoliths followed by an application of        the Zr-based primer.

The metal monoliths, with 0% wall porosity, and the ceramic substrates,with very low wall porosity, were pre-treated before coating to increaseadhesion of the adsorbent layer and, thus, increase the lifetime of thestructured adsorbent.

The surface of the metal monoliths were modified by a high temperature(i.e., ˜900° C.˜1050° C., for ˜6 hours) thermal treatment in air todevelop a micron-thin metal oxide skin, useful for roughening thesurface and creating anchoring sites. An SEM image of the ˜1440 cpsimetal monolith after pre-treatment at ˜900° C. is shown in FIG. 3.Following this process, a thin coating of a Zr-based oxide (Aremco644-N, diluted with 12% H₂O), was applied by a dip-coating process toapply the primer layer.

The surface of the ceramic monoliths were primed with the Aremco 644-Nto increase surface roughness and anchoring sites on the glass-like,very low porosity walls to improve adhesion of the adsorbent layer.

3. Coating Slurry Preparation

An aqueous slurry was prepared with ˜35 weight % solids content byadding deionized water (˜40.413 g), colloidal SiO₂ (Nissan Chemicals US,MP-1040, ˜100 nm diameter SiO₂, ˜40 wt % solids, ˜5.942 g), DDRadsorbent (prepared according to the methods described in U.S. PatentApplication Publication No. 2014/0161717) (˜25 μm to ˜30 μm averagediameter particles, 22.050 g), ˜0.5% sodium silicate solution (EMDCorp., ˜29% SiO₂, ˜9% Na₂O, ˜0.253 g), ˜2 wt % of 2% aqueous methylcellulose solution (Dow Methocel ˜240 S, ˜1.422 g) and ˜3 mole %methanol (˜2.43 gm methanol). FIGS. 4-6 provide transmission electronmicroscopy (TEM) images and particle diameter graphs of the ˜100 nmcolloidal SiO₂ binder used as well as other binders utilized,specifically ˜25 nm colloidal SiO₂, and string of pearls colloidal SiO₂.

The methyl cellulose was used for viscosity control, slurrystabilization, to aid in uniform film formation, and as a lubricityagent to improve removal of excess slurry in ultra-fine channels thathave associated very high capillary forces. Methanol was used to aidparticle dispersion (to avoid particle agglomeration) due to its surfaceactivity. The ratio of DDR adsorbent to total SiO₂ added was ˜90:10weight/weight. The slurry was mixed using a FlackTek asymmetriccentrifugal lab mixer for ˜1 minute at ˜2200 rpm to obtain ahomogeneously dispersed mixture. The prepared slurry had a viscosity of˜14 cP and a final pH of approximately 11.

Coating

The ultra-high density monoliths were dipped into a well-mixed slurry ofapproximately 35 wt % solids for less than a minute. Other techniquesthat can be used to immerse the monolith cells in slurry can includemild vacuum technique, pulling slurry up into the cells, and pumping theslurry into the monolith cells from above, inside a closed plasticvessel.

Excess slurry was removed from the cells using a high velocity nitrogengas flow (approximately 200 L/min flow rate) for several minutes. Thehigh flow gas purge resulted in rapid evaporative cooling of the slurryin the channels. Plugging of the channels by dried slurry was observed.Without being bound by theory, it is believed that the evaporativecooling led to slower water evaporation and drying of the residualcoating on the monolith wall. After discontinuing the gas purge, themonoliths statically air dried for hours (˜3 to ˜6 hours) in a verticalposition.

After removal of excess slurry in the monolith channels, the monolithswere flash dried, to stabilize the films and prevent “bridging” and sizesegregation of the zeolite and binder particles on vertical standing.After the channels were initially cleared with a high flow gas purge,the gas stream was then heated with an in-line Osram heater to 50-60° C.to rapidly dry and stabilize films on the cell walls. The coating wasdried in-situ for several minutes. The monoliths were then calcined inair to 500° C. using a heating ramp: a) 120° C. drying for 8 hrs, b)increase temperature to 500° C. over 4 hours, c) holding at 500° C. for2 hours, and d) cooling to 120° C. in 2 hours. FIG. 7 shows a LeicaOptical scope picture (40× magnification) of the 1440 cpsi metalmonolith after 4 coatings with DDR (25-30 μm) and SiO₂ (100 nm), afterremoval of excess slurry and 500° C. calcination. FIG. 8 provides an SEMimage of the DDR (25-30 μm) and SiO₂ (100 nm) coating on the 1440 cpsimetal monolith and/or a glass slide after 500° C. calcination.

Example 2—Integrity Testing of Coupons

Samples of test coupons were prepared and sent to Southwest ResearchInstitute (SWRI), an independent lab, for coating integrity testing. Theobjective was to test the integrity of a washcoat coating on severaltest coupons under conditions of rapid pressurization anddepressurization. During the testing, each coupon was individuallyinstalled into a test rig capable of rapid pressurization anddepressurization. During the testing, a total of 24 pressure cycle testswere performed on six test coupons at five pressure conditions.

Sample Preparation

The substrate coupons used were polished 316 stainless steel (#8finish), ˜3.25″ L×˜0.5″ W×˜0.060″ thick strips with 2 holes measuring˜0.12 inches in diameter drilled into each coupon for mounting to thetest rig.

A ˜69 wt % solids aqueous slurry was made by mixing ˜1.4 grams of DDRzeolite (˜10 μm to ˜15 μm) prepared according to the methods describedin U.S. Patent Application Publication No. 2014/0161717) and 1.526 gramsof colloidal silica (˜25 nm, 40 wt % solids, Aremco 644 S) to form asemi-paste. The paste, representative of the active components in awashcoating slurry, were applied to the coupons with a doctor-bladetechnique. The coated coupons were air dried at room temperatureovernight. They were subsequently dried at ˜120° C. for ˜1 day.

Four sets (A-D) of duplicate samples were prepared by applying slurryabove to coupons. Descriptions of the final coupons and labels arebelow:

-   -   NB 26027-25-2-2 samples: no pre-thermal oxidation        treatment+Zr-silicate primer coating (Aremco 644-N material);    -   26-6-2 samples: ˜900° C. oxidized coupon+Zr-silicate primer        coating (Aremco 644-N material);    -   26-7-3 samples: ˜900° C. oxidized coupon+no Zr primer        coat+DDR/SiO₂ (˜25 nm) having a ration of 70:30 w/w.    -   26-8-23 samples: ˜900° C. oxidized coupon+Zr-silicate primer        coating+DDR/SiO₂ (˜25 nm) having a ratio of ˜70:30 w/w;    -   25-4-23 samples: no pre-thermal oxidation treatment+Zr-silicate        primer coating+DDR/SiO₂ (˜25 nm) having a ratio of ˜70:30 w/w.        A picture of the samples as prepared is shown in FIG. 9. The        circled letter indicates which samples were tested.

Test Procedure (SwRI)

The following test procedure was performed on the coupons:

-   -   1. The initial weight of the each coupon was recorded.    -   2. The coupons were loaded into the test rig and the following        conditions were tested on each coupon in Table 1:

TABLE 1 Test Summary NUMBER OF LOW TEST CYCLES PER HIGH PRESSUREPRESSURE CONDITION COUPON (psia) (psia) Base 1 250 783 653 Base 2 250783 435 Base 3 250 783 218 Stepout 1 250 943 218 Stepout 2 20 1230 218

-   -   3. After each test condition was complete, each coupon was        removed from the rig and allowed to sit for at least 5 minutes        to allow equilibration with room humidity. The mass of the        coupons were taken by leaving the coupons on the scale for about        30 seconds to determine if the coupon was gaining mass through        water absorption. Once mass gain had ceased, the mass for the        coupons was recorded.

There was no significant weight loss for any of the coupons during thecourse of testing as shown in Tables 2 and 3 below.

TABLE 2 Weight after Testing RECORDED WEIGHT (g) TEST AFTER AFTER COU-INITIAL AFTER AFTER AFTER STEPOUT STEPOUT PON WEIGHT BASE 1 BASE 2 BASE3 1 2 26-8- 12.0983 12.0983 12.0985 12.0995 12.0990 12.0992 23C 25-4-11.9207 11.9210 11.9211 11.9225 — — 23C 26-7-3C 12.1812 12.1812 12.181612.1827 — —

TABLE 3 Change in Test Coupon Weight INITIAL INITIAL WEIGHT CHANGE FROMINITIAL (g) TEST WEIGHT WEIGHT AFTER AFTER AFTER AFTER AFTER COUPON (g)RANGE (g) BASE 1 BASE 2 BASE 3 STEPOUT 1 STEPOUT 2 26-8-23C 12.09830.0010 0.0000 0.0002 0.0012 0.0007 0.0008 25-4-23C 11.9207 0.0010 0.00030.0004 0.0018 — — 26-7-3C 12.1812 0.0009 0.0000 0.0004 0.0015 — —Variation in coupon weight was observed, but these variances were on thesame order of magnitude as those observed during the initial fourweights obtained on each untested coupon.

No visual indications of coating damage or loss were seen during thecourse of these experiments, as can be seen FIGS. 10-12, which providescomparison photographs of the coupons take before (top photograph) andafter testing (bottom photograph).

Example 3—Integrity Testing of Coatings on Coated Monoliths

A ˜2390 cpsi 316 stainless steel monolith (1.1″ d×3″ L) was oxidized at˜900° C. for ˜6 hr, primed with a Zr-silicate coating and dip coatedmultiple times in a slurry of DDR (˜25 μm) prepared according to themethods described in U.S. Patent Application Publication No.2014/0161717 (25 nm Aremco 644-S colloidal SiO₂). After 500° C.calcination, the adsorbent coating matrix, was 20% by total weight andthe resultant coated monolith was mounted on metal disc resulting intest button D.

Pressure swing cycles were conducted on the washcoated monolith usingthe Test Rig for adsorptive kinetic separation (TRAKS). These tests weredone at a adsorptive kinetic separation (AKS) pilot plant with gasvelocities up to ˜20 ft/s and pressure drops up to ˜15 bar-a. As shownin FIG. 13 (pictures of test button D before and after testing) and FIG.14 (weight of test button D as superficial gas velocity increases), nosignificant amount of wash-coat was lost during testing. The resultsindicate that the washcoat matrix on the monolith is robust enough towithstand AKS operating conditions.

Example 4—Activity Testing of Coatings

Samples of the washcoating matrix were processed for activity testing.Aqueous slurries were prepared with ˜50 weight % solids content, asdescribed in Example 1 above. The slurries were caste onto glass plates(˜12″×˜12″) and air dried overnight (˜8 to ˜16 hours) to form a whitecolored film on the glass. The sample was then dried at ˜120° C. for ˜8hours. The samples were removed from the glass plates and the shards ofsamples were calcined to ˜500° C. for ˜4 hours. A portion of the sampleswere then ground to a powder and sieved to ˜75-˜150 μm for activitytesting by Zero Length Chromotography (ZLC) substantially according tothe method described in U.S. patent application Ser. No. 14/573,177.

The samples tested are summarized below in Table 4.

TABLE 4 Samples for Activity Testing 1 DDR (25 um avg) 13-49 prep 13-66*25 nm Aremco SiO2 +0.5% Na-Silicate +no viscosifier 2 DDR (25 um avg)13-49 5 prep 13-66 *25 nm Aremco SiO2 +0.0% Na-Silicate +no viscosifier3 DDR (25 um avg) 13-49 prep 13-66 *100 nm nm SiO2 +0.5% Na-Silicate+viscosifier 4 DDR (25 um avg) 13-49 prep 13-66 *string of pearls SiO2+0.5% Na-Silicate +viscosifier 5 DDR (25 um avg) 13-49 0 prep 13-69 *25nm Aremco SiO2 +0.0% Na-Silicate +no viscosifier 6 DDR (25 um avg) 13-490 prep 13-69 *100 nm nm SiO2 +0.5% Na-Silicate +viscosifier 7 DDR (25 umavg) 13-49 prep 13-69 *string of pearls SiO2 +0.5% Na-Silicate+viscosifier

ZLC Measurement

Samples were tested by ZLC to determine if the additives in the coatingmatrix (e.g., SiO₂ binders and other additives) affected the kinetics ofthe adsorbent. As shown in FIGS. 15 and 16, there was minimal effect onmethane diffusivity due to the diameter or amount of silica binder inthe coating matrix samples compared to a DDR adsorbent (“parent DDR”)which was steamed at 1050° C. As determined from FIGS. 15 and 16, theparent DDR had a diffusivity of 4.4 E-14 m2/s and the coating matrixsamples with DDR bound with SiO₂ had a diffusivity of 4.0-4.6 E-14 m2/s.

Samples made with “string of pearls” (i.e., 4 and 7) exhibit a slightlylower methane diffusivity, suggesting a slight selectivation effect bythis type of binder.

1. A structured adsorbent bed for purification of a gas feedstreamcomprising: a substrate having a cell density greater than 1040 cellsper square inch (cpsi); and a coating on the substrate, wherein thecoating comprises adsorbent particles and a binder.
 2. The structuredadsorbent bed of claim 1, wherein the adsorbent particles have anaverage diameter of about 2 μm to about 40 μm.
 3. The structuredadsorbent bed of claim 1, wherein the adsorbent particles have anaverage diameter greater than about 20 μm.
 4. (canceled)
 5. Thestructured adsorbent bed of claim 1, wherein the adsorbent particlescomprise a microporous material.
 6. The structured adsorbent bed ofclaim 5, wherein the microporous material comprises a zeolite.
 7. Thestructured adsorbent bed of claim 6, wherein the zeolite is DDR.
 8. Thestructure adsorbent bed of claim 7, wherein the zeolite is selected fromthe group consisting of Sigma-1 and ZSM-58.
 9. The structured adsorbentbed of claim 1, wherein the binder comprises particles having an averagediameter of about 25 nm to about 200 nm.
 10. The structured adsorbentbed of claim 1, wherein the binder comprises particles having an averagediameter of about 100 nm to about 200 nm.
 11. The structured adsorbentbed of claim 1, wherein the binder has a pH greater than
 7. 12. Thestructured adsorbent bed of claim 1, wherein the binder comprises SiO₂.13. The structured adsorbent bed of claim 1, wherein the substrate has acell density of about 1500 cpsi to about 4000 cpsi.
 14. The structuredadsorbent bed of claim 1, wherein the substrate has a cell density ofabout 1400 cpsi or greater.
 15. The structured adsorbent bed of claim 1,wherein the coating on the substrate has a thickness of about 30 μm toabout 200 μm.
 16. The structured adsorbent bed of claim 1, wherein thecoating on the substrate has a thickness of at least 100 μm or greater.17. The structured adsorbent bed of claim 1, wherein the coatingcomprises one or more layers of adsorbent particles and binderparticles.
 18. The structured adsorbent bed of claim 1, wherein thesubstrate is a porous solid selected from the group consisting of ametal oxide, a mixed-metal oxide, a ceramic and a zeolite.
 19. Thestructured adsorbent bed of claim 18, wherein the substrate has aporosity of about 6% or less.
 20. The structured adsorbent bed of claim1, wherein the substrate is a non-porous solid selected from the groupconsisting of a metal, a glass and a plastic.
 21. The structuredadsorbent bed of claim 20, wherein the metal is stainless steel.
 22. Thestructured adsorbent bed of claim 1 further comprising azirconium-containing layer on the substrate
 23. A method of preparingthe structured adsorbent bed of claim 1, the method comprising:pretreating the substrate; preparing an aqueous slurry comprising theadsorbent particles and the binder; and applying the aqueous slurry tothe substrate to form the coating on the substrate.
 24. The method ofclaim 23, wherein pretreating the substrate comprises: (i) applying azirconium-containing layer to the substrate; or (ii) heating thesubstrate and applying the zirconium-containing layer to the substrate.25. The method of claim 24, wherein (ii) heating the substrate isperformed at about 600° C. to about 1100° C.
 26. The method of claim 24,wherein the zirconium-containing layer comprises zirconium oxide,zirconium silicate or a combination thereof.
 27. The method of claim 23,wherein the binder is SiO₂.
 28. The method of claim 23, wherein theweight ratio of the adsorbent particles to the binder is from about70:30 w/w to about 90:10 w/w.
 29. The method of claim 23, furthercomprising: removing excess coating from the coated substrate; dryingthe coated substrate; and heating the coated substrate.
 30. The methodof claim 29, wherein the excess coating is removed from the substrate byflowing a gas through the coated substrate at a rate equal to or greaterthan 100 L/min.
 31. The method of claim 29, wherein drying the coatedsubstrate comprises flash drying the coated substrate wherein a gaspurge heated from about 50° C. to about 60° C. is flowed through thecoated substrate at rate of at least about 100 L/min.
 32. The method ofclaim 23, wherein the coating has about 10% to about 40% macroporosity.33. A gas separation process comprising contacting a gas mixturecontaining at least one contaminant with the structured adsorbent bed ofclaim
 1. 34. The process of claim 33, wherein the gas mixture comprisesCH₄.
 35. The process of claim 33, wherein the at least one contaminantis selected from the group consisting CO₂, H₂O, H₂S, NO_(x) and SO_(x).36. The gas separation process of claim 33, wherein the processcomprises PSA, TSA, PPSA, PTSA, RCPSA, RCTSA, RCPPSA or RCPTSA.